1. Field of the Invention
The present invention relates to a laminated coil component, and in particular, to an open-magnetic-circuit-type laminated coil component.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2001-44037 describes an open-magnetic-circuit-type laminated coil component in which a magnetic layer is provided on both main surfaces of a non-magnetic layer to improve the direct-current superposition characteristic. However, when the non-magnetic layer and the magnetic layers are fired in a laminate, Ni included in the magnetic layers diffuses into the non-magnetic layer. More specifically, the non-magnetic layer is made of Zn—Cu ferrite and the magnetic layers are made of Ni—Zn—Cu ferrite or Ni—Zn ferrite, and thus, Ni included in the magnetic layers diffuses into the non-magnetic layer. Consequently, the non-magnetic layer into which Ni is diffused becomes a magnetic material, and thus, the thickness of the layer functioning as the non-magnetic layer decreases. This decreases the effect of improving the direct-current superposition characteristic due to the open-magnetic-circuit structure (non-magnetic interlayer structure).
A factor that affects the amount of diffusion of Ni into the non-magnetic layer is the firing temperature. Furthermore, variations in the firing temperature among production lots cause variations in the inductance characteristic of the laminated coil components and variations in the direct-current superposition characteristic. This problem becomes more serious as the size of the laminated coil component is reduced.